1. Field of the Invention
This invention relates to means for controlling the fuel/air mixture for an internal combustion engine and has particular reference to means for improving the performance of a supercharged engine from an idling condition to a high speed condition.
2. Description of the Prior Art
It is well known that superchargers are very effective in increasing the power of an internal combustion engine. Therefore, smaller engines having superchargers associated therewith can do work previously requiring much larger, heavier and more expensive engines. However, there are certain drawbacks which have heretofore discouraged widespread use of superchargers for engines which are primarily used to power automobile, boat and similar engines wherein the speed of the engine must be often varied between idling and high speed. Among such drawbacks is the fact that when the supercharger is connected to draw an air/fuel mixture from the carburetor and to force the same through the intake manifold of the engine, the mixture must travel over a relatively long distance. During such travel, when the engine is idling and the fuel/air mixture is moving at a low velocity, the fuel, such as gasoline, tends to precipitate out of the mixture in liquid form and to collect on the walls of the induction duct work or conduit. This is augmented by the fact that a relatively high vacuum exists in the induction conduit during idling, thus lowering the temperature of the mixture. Such fuel drop-out tends to cause erratic idling operation and also, when the engine is accelerated from idling condition, the accumulated liquid fuel is picked up by the air flow, making an over-rich mixture which again tends to cause erratic operation during the transition from idling speed to normal or high speed.
Heretofore, attempts to correct the above condition comprised, for example, providing a special pump and conduit to pick up the collected liquid fuel and to introduce the same into the intake manifold (see the U.S. Pat. No. 3,910,849 to R. J. Lloyd). Another solution has been to provide means for heating the mixture during its travel from the carburetor to the inlet of the supercharger compressor. However, since the mixture is later further heated by compression as it leaves the compressor on its way to the intake manifold, the overall rise in temperature of the mixture reaches a level where it tends to cause dangerous heating and detonating effects with consequent loss of power and internal damage when introduced into the combustion chambers of the engine. In order to overcome the latter condition, air coolers, as disclosed in the U.S. Pat. No. 2,292,233 to A. Lysholm, have been employed to cool the mixture prior to entry into the intake manifold. Although such coolers are usually satisfactory, they present added weight, bulk, complexity and cost.
The foregoing problems have been recognized heretofore and efforts to shorten the path of delivery of the fuel/air mixture between the carburetor and the intake manifold during idling conditions have been attempted. For example, in the U.S. Pat. No. 3,868,822 to R. A. Keller, a relatively short induction conduit is provided between the carburetor and the intake manifold, with a floating one-way valve therein, and with the supercharger compressor inlet connected upstream from the valve and the compressor outlet connected downstream from the valve. Although this arrangement is generally satisfactory, the valve is subject to fluttering due to rapid changes in air pressure, tending to cause excessive wear and damage to the valve and possible ingestion into the engine.
An additional problem encountered in the association of superchargers, particularly turbochargers, with internal combustion engines is the fact that at higher speeds the supercharger compressor tends to supply more pressurized air than is required for proper operation, thus abnormally raising the boost pressure. Generally, this has been corrected in a turbocharger by the incorporation of a waste gate valve in the turbine drive circuit which automatically opens when the pressure exceeds a predetermined amount. Since the waste gate valve is in the path of the relatively hot and corrosive exhaust gasses, it is subject to malfunction and deterioration.